Positive electrode active material for non-aqueous electrolyte secondary battery and production method for same, precursor for positive electrode active material, and non-aqueous electrolyte secondary battery using positive electrode active material

ABSTRACT

Provided is a cathode active material for a non-aqueous electrolyte secondary battery capable of obtaining high initial discharge capacity and good output characteristics at low temperature. In order to achieve this, a cathode active material that is a lithium nickel composite oxide composed of secondary particles that are an aggregate of primary particles is expressed by the general expression: Li w (Ni 1-x-y Co x Al y ) 1-z M z O 2  (where 0.98≦w≦1.10, 0.05≦x≦0.3, 0.01≦y≦0.1, 0≦z≦0.05, and M is at least one metal element selected from a group consisting of Mg, Fe, Cu, Zn and Ga), and where the crystallite diameter at (003) plane of that lithium nickel composite oxide that is found by X-ray diffraction and the Scherrer equation is within the range of 1200 Å to 1600 Å is used as the cathode material.

TECHNICAL FIELD

The present invention relates to a non-aqueous electrolyte secondarybattery, a cathode active material that is used as the cathode materialin that non-aqueous electrolyte secondary battery, a manufacturingmethod for that cathode active material, and a precursor that is used inthe manufacture of that cathode active material. More specifically, thepresent invention relates to cathode active material composed of alithium nickel composite oxide, a non-aqueous electrolyte secondarybattery that uses that cathode active material as the cathode, amanufacturing method for the lithium nickel composite oxide, and anickel composite hydroxide as a precursor to the lithium nickelcomposite oxide.

BACKGROUND ART

In recent years, secondary batteries such as non-aqueous electrolytesecondary batteries or nickel-metal hydride batteries have becomeimportant as the power source mounted in automobiles using electricityas the driving source, or as the power source mounted in personalcomputers or mobile terminal and other electrical products.Particularly, it is expected that non-aqueous electrolyte secondarybatteries that are lightweight and have a high energy density will besuitably used as a high output power source for use in automobiles.

In the construction of a typical lithium ion secondary battery as anon-aqueous electrolyte secondary battery, there is provided anelectrode active material layers on the surface of an electrodecollector that capable of reversible occlusion and discharge of lithiumions, and more specifically, there is provided a cathode active materiallayer and anode active material layer. For example, in the case of thecathode, cathode active material that is composed of a composite oxidethat includes transition metals such as lithium, nickel and the like asmetal elements are dispersed in to a suitable solvent that is composedof an aqueous solvent such as water or various kinds of organic solventto obtain a paste-like composition or slurry-like composition(hereafter, these composition will simply be referred to as “paste”),and a cathode active material layer is formed by applying that paste toan electrode collector.

Incidentally, of the composite oxides of a cathode active material of alithium ion secondary battery, a so-called lithium nickel compositeoxide constructed with nickel as the main material: LiNi_(1-x)M_(x)O₂ (Mis one kind or two or more kinds of metal elements other than nickel)has advantages over conventional lithium cobalt composite oxides in thatit theoretically has greater lithium ion occlusion capacity, and it ispossible to reduce the amount of costly metal material such cobalt thatis used, so is gaining much attention as a suitable cathode material forthe construction of a lithium ion secondary battery.

When using a lithium nickel composite oxide, which is obtained by aconventionally proposed manufacturing method, as a cathode activematerial, there is a problem in that even though the charge capacity anddischarge capacity is higher than that of a lithium cobalt oxide, thecyclability is inferior. Moreover, when used in high-temperatureenvironments or low-temperature environments, lithium nickel compositeoxide has a disadvantage in that it is comparatively easy for thebattery performance to become impaired.

In order to improve cyclability, adding or substituting different kindsof elements into the lithium nickel composite oxide is being tried. Forexample, JP 8-78006 (A) discloses a cathode active material that iscomposed of a composite oxide having layered structure and expressed bythe general expression: Li_(a)Ni_(b)M¹ _(c)M²O₂, where M¹ is Co, and M²is one or more kind of element that is selected from among at least B,Al, In and Sn.

With the cathode active material of this disclosure, the cyclability isimproved, however, depending on the existence of added elements, thecapable range of intercalation and deintercalation of lithium ions ofthe cathode active material becomes narrow, so there is a tendency forthe discharge capacity to decrease. This decrease in discharge capacityis known to become particularly remarkable in heavy load conditionswhere the discharge current is large, or in low-temperature efficientdischarge conditions where the mobility of electrolytes becomes small atlow temperature.

The output characteristics at high temperature or low temperature ofsecondary battery are extremely important characteristics when thebattery is used in equipment that is used in environments where there isa large change in temperature, and particularly when considering use ancold regions, it is necessary for the battery to have sufficient outputcharacteristics at low temperature.

In an attempt to improve the output characteristics at low temperature,JP 11-288716 (A) discloses a cathode active material that is composed oflithium nickel cobalt oxide formed of spherical or elliptical secondaryparticles having an average particle size of 5 μm to 20 μm and in whichprimary particles are collected in a radial fashion, with this cathodeactive material being expressed by the general expression:Li_(x)Ni_(y)Co_(1-y)O₂ (where 0<x<1.10, 0.75<y<0.90),

With the cathode active material of this disclosure, uniformintercalation and deintercalation from the surface of the secondaryparticles to inside the crystal is possible, and a lithium ion secondarybattery having high capacity, excellent heavy load characteristics andexcellent low-temperature efficient discharge characteristics can beobtained. However, when the cathode active material described above isused, the surface of the secondary particles is covered by conductivematerials, binding agent, or gas that is adsorbed into the surface thesecondary particle during the formation of the cathode active material,so mobility of the lithium ions is obstructed, it is feasible thatparticularly low-temperature efficient discharge characteristics willnot be sufficiently obtained.

On the other hand, in attempts to improve the large current charge anddischarge characteristics, or in other words, improve the outputcharacteristics, attention has been placed on the size of the primaryparticles and secondary particles of the cathode active material. Forexample, JP 2000-243394 (A) discloses that by keeping the ratio “D50/r”of the average length “r” in the short length direction of the primaryparticles, and the particle size “D” when the volume cumulativefrequency of particle size distribution of secondary particles reaches50% within a specified range, cathode active material having highdischarge potential, excellent large current characteristics and goodcyclability can be obtained.

The crystallinity of the cathode active material is also described,where preferably the relationship between the half width (full width athalf maximum) FWHM (003) and FWHM (104) of the diffraction peaks of the(003) surface and (104) surface of the Miller indices hk1 of X-raydiffraction of composite oxide that can be used as a cathode activematerial is 0.7≦FWHM (003) FWHM (104)≦0.9, and furthermore, preferably,0.1°≦FWHM (003)≦0.16° and 0.13°≦FWHM (104)≦0.2°.

These indicate the effect of the crystallinity of the cathode activematerial on the output characteristics, however, they are related to therelationship between the large charge and discharge characteristics andthe relative orientation of a plurality of crystal surfaces, and thereis no mention of improvement of the low-temperature output.

Moreover, JP 10-308218 (A) discloses a cathode active material for alithium ion secondary battery that is expressed by the generalexpression: LiMO₂ (where M is at least one element selected from amongthe group of Co, Ni, Fe, Mn and Cr), and is composed of particles thatare a collection of single crystals with minute crystallites as theunit, where the shapes of the crystallites and the particles aresterically nearly isotropic in shape, and when expressed in term ofcrystallites, is within the range of 500 Å (Angstroms) to 750 Å in the(003) vector direction and 450 Å to 1000 Å in the (110) vectordirection.

In this disclosure, the size of the crystallites is used for expressingthe sterical isotropic shape of the particles, however, there is nomention of the effect of the size of the crystallites themselves.Moreover, the object is to achieve both thermal stability duringcharging and good charge and discharge cyclability; and is not relatedto an improvement in low-temperature output.

On the other hand, attempts are being made to improve the cathode activematerial by placing attention on the nickel composite compound used asthe raw material for the lithium nickel composite oxide, or in otherwords the characteristics of the precursor of the cathode activematerial. As the method for manufacturing the lithium nickel compositeoxide, a typical method of mixing and calcining a lithium compound and anickel composite compound that is composed of nickel, cobalt and metalelements M is used. Hydroxides, oxides, nitrates and the like are usedin the nickel composite compound, however, because it is easy to controlthe shape, particle size and crystallinity of the materials, typically ahydroxide or an oxide that is obtained by calcining the hydroxide isused.

For example, JP 7-335220 (A) discloses manufacturing a cathode activematerial composed of lithium nickel oxide that is expressed by thegeneral expression LiNiO₂, wherein the lithium nickel oxide is obtainedby performing heat treatment in an oxidizing atmosphere of nickelhydroxide and lithium hydroxide that are formed into secondary particlesthat are a collection of primary particles having a particle size of 1μm or less.

Furthermore, by using a particle structure in which the opening sectionof the primary particles having a layered structure of nickel hydroxideis oriented toward the outside of the secondary particles, the endsurface of the generated LiNiO₂ layer also maintains that shape and isoriented toward the outside of the powdered particles, so intercalationand de-intercalation of Li during charging and discharging can advancesmoothly.

However, in this disclosure, only the particle shape of the cathodeactive material that is obtained and maintaining the orientation isdisclosed, and there is no mention of the effect of nickel hydroxides onthe crystallinity of the cathode active material that is obtained.

Moreover, JP 11-60243 (A6) discloses a nickel hydroxide as a precursorto a cathode active material that is expressed by the generalexpression: Ni_(1-y)A_(x)(OH)₂ (where A is cobalt or manganese,0.10<x<0.5), and is composed of a layered body having uniform crystalorientation or a single crystal, with particle size of primary particlesbeing 0.5 to 5 μm, and the full width at half maximum found throughX-ray diffraction obtained by taking a sampling with the easiestorientation is (001)<0.3 deg., (101)<0.43 deg., and the peak intensityratio is I (101)/I (001)<0.5.

In the case of this disclosure, the thermal characteristics duringcharging are improved by achieving the accretion of primary particles inthe raw material stage instead of by sintering during calcination, andwithout a decrease in battery characteristics of the lithium ionsecondary battery. However, nothing is mentioned about the crystallinityof the obtained cathode active material, or about the effectcrystallinity of nickel hydroxide as a raw material, and does notmention anything about improving the low-temperature output.

Furthermore, the relationship between the battery characteristics of acathode active material and the power characteristics of the material isbeing studied. For example, the applicants of this disclosure proposedin JP 2000-30693 (A) a hexagonal lithium nickel composite oxide having alayered structure that is expressed as[Li]_(3n)[Ni_(1-x-y)Co_(x)Al_(y)]_(3b)[O₂]_(6c) (where the subscripts tothe brackets [ ] represent sites, and x and y satisfy the conditions0<x≦0.20, and 0<y≦0.15), and with the objective of reducing irreversiblecapacity, the structure is such that secondary particles are formed bycollecting a plurality of primary particles of the lithium nickelcomposite oxide, with the average particle size of the primary particlesbeing 0.1 μm or greater. Moreover, it is disclosed that there is alinear correlation between the average particle size of the primaryparticles and the crystallite diameter that is calculated from the halfwidth of the 003 peak in the X-ray diffraction pattern, with thecrystallite diameter that is calculated from the half width of the 003peak in the X-ray diffraction pattern being 40 nm (400 Å) or greater,and more specifically, within the range of 430 Å to 1190 Å.

However, in that disclosure, regulating the powder characteristics ofthe battery characteristics because of its relationship to the reductionin irreversible capacity of the battery is disclosed, however, therelationship between the low-temperature output and the powdercharacteristic is not studied, and nothing is disclosed for improvingthe low-temperature output.

RELATED LITERATURE Patent Literature

-   [Patent Literature 1] JP 8-78006 (A)-   [Patent Literature 2] JP 11-288716 (A)-   [Patent Literature 3] JP 2000-243394 (A)-   [Patent Literature 4] JP 10-308218 (A)-   [Patent Literature 5] JP 7-335220 (A)-   [Patent Literature 6] JP 11-60243 (A)-   [Patent Literature 7] JP 2000-30693 (A)

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

The object of the present invention is to provide a cathode activematerial for a non-aqueous electrolyte secondary battery that makes itpossible to obtain a battery that has good output characteristics in ahigh-temperature environment or low-temperature environment, andparticularly in a low-temperature environment, while at the same time iscapable of maintaining battery characteristics such as thecharge/discharge capacity and cyclability.

Means for Solving the Problems

In order to solve the problems described above, the inventors diligentlystudied improvement of the output characteristics of a non-aqueouselectrolyte secondary at low temperature. As a result, it was found thatby distributing pores having a certain size inside of which electrolytecan penetrate in the cathode active material, it is possible to improvethe low-temperature output characteristics, and the size of the porescan be regulated by making the crystallite diameter of the lithiumnickel composite oxide of the cathode active material a certain size.Furthermore, it was learned that there is a close correlation betweenthe crystallinity of the nickel composite hydroxide as precursor and thecrystallinity of the lithium nickel composite oxide that is finallyobtained, and that cathode active material above can be obtained bycontrolling the half width (full width at half maximum) of a specifiedcrystal surface of the nickel composite hydroxide. The inventorsachieved the invention based the knowledge they gained.

In other words, the cathode active material for a non-aqueouselectrolyte secondary battery of the present invention is a lithiumnickel composite oxide composed of secondary particles that are anaggregate of primary particles and is expressed by the generalexpression: Li_(w)(Ni_(1-x-y)Co_(x)Al_(y))_(1-z)M_(z)O₂ (where0.98≦w≦1.10, 0.05≦x≦0.3, 0.01≦y≦0.1, 0≦z≦0.05, and M is at least onemetal element selected from a group consisting of Mg, Fe, Cu, Zn andGa).

Particularly, in the cathode active material for a non-aqueouselectrolyte secondary battery of the present invention, the crystallitediameter at (003) plane of the lithium nickel composite oxide that isfound by X-ray diffraction and the Scherrer equation is within the rangeof 1200 Å to 1600 Å, and preferably is within the range of 1200 Å to1500 Å.

The precursor for obtaining the cathode active material for anon-aqueous electrolyte secondary battery of the present invention isnickel composite hydroxide expressed by the general expression:(Ni_(1-x-y)Co_(x)Al_(y))_(1-z)M_(z)(OH)₂ (where 0.05≦x≦0.3, 0.01≦y≦0.1,0≦z≦0.05, and M is at least one metal element selected from a groupconsisting of Mg, Fe, Cu, Zn and Ga), and where the half width at (101)plane found by X-ray diffraction is 0.45° to 0.8°, and by mixing theprecursor for obtaining a cathode active material for a non-aqueouselectrolyte secondary battery with a lithium compound or by mixing theprecursor after oxidizing roasting with a lithium compound, andperforming calcination of the obtained mixture in an oxidizingatmosphere, the cathode active material for a non-aqueous electrolytesecondary battery of the present invention is obtained.

Moreover, preferably, the precursor is obtained by covering the surfaceof a hydroxide composed of Ni, Co and M given by the expression abovewith aluminum hydroxide.

In the manufacturing method for the cathode active material for anon-aqueous electrolyte secondary battery of the present invention, theprecursor, or an oxide of the precursor that is obtained by performingoxidizing roasting of the precursor is mixed with a lithium compound andthe obtained mixture is calcinated in oxidizing atmosphere to obtain alithium nickel composite oxide. Preferably, the calcination temperatureis within the range 700° C. to 760° C., and lithium hydroxide is used asthe lithium compound.

In the non-aqueous electrolyte secondary battery of the presentinvention, a cathode active material layer, which is formed from thecathode active material for a non-aqueous electrolyte secondary batteryhaving the composition and characteristics above, is formed on a cathodecollector.

Effect of the Invention

By using the cathode active material for a non-aqueous electrolytesecondary battery of the present invention, it is possible to obtain anon-aqueous electrolyte secondary battery having good outputcharacteristics at low temperature. The cathode active material of thepresent invention having such characteristics can be easily obtained byusing the precursor of the present invention. Therefore, the industrialvalue of the present invention can be said to be very large.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the relationship between thecrystallite diameter on the (003) surface of a lithium nickel compositeoxide and the −30° C. low-temperature output.

MODES FOR CARRYING OUT THE INVENTION

Charging and discharging of a lithium ion secondary batters which is anon-aqueous electrolyte secondary battery that uses a lithium nickelcomposite oxide as a cathode active material proceeds by lithium ionmoving between the cathode active material and the electrolyte, and thelithium ions irreversibly leaving and entering the cathode activematerial. Therefore, the ease of movement of lithium ions duringcharging and discharging, or in other words, the mobility thereoflargely affects the charge and discharge characteristics of a secondarybattery, and particularly affects the output characteristics and ratecharacteristics thereof.

Movement of lithium ions can be divided into movement inside the cathodeactive material, movement at the boundary between the cathode activematerial and the electrolyte, and movement inside the electrolyte,however, movement inside the electrolyte depends on the electrolyte soit is not related to the cathode active material.

As described above, movement of lithium ions is performed through theboundary between the cathode active material and electrolyte, so themobility of lithium ions at this boundary greatly affects the internalresistance of the battery. In other words, when the mobility of lithiumions at this boundary is low, the internal resistance becomes high, andit is not possible to display good output characteristics as a battery.

Particularly, in a low-temperature environment, the rate of diffusion oflithium into the electrolyte decreases together with the mobility oflithium ions at the boundary between the cathode active material and theelectrolyte. Therefore, in order to obtain a secondary battery havinghigh output characteristics at low temperature, it is necessary toobtain a cathode active material that has small resistance even at lowtemperature, or in other words, it is necessary to obtain a secondarybattery that uses a cathode active material that has high mobility oflithium ions at this boundary.

The mobility of lithium ions at the boundary between the cathode activematerial and the electrolyte depends on the insertion and extraction oflithium ions from the surface of the cathode active material, however,as long as the insertion and extraction per unit area is the same, themobility depends on the surface area at this boundary. In other words,the larger the surface area of the surface of the cathode activematerial is, the larger the contact area between the cathode activematerial and the electrolyte becomes, which is advantageous for themovement of lithium ions during charging and discharging.

Here, the surface area of the cathode active material surface means thesurface area of the portion that comes in contact with the electrolyte.In other words, the area of portions of minute pores is included in thesurface area when the surface area is measured by the nitrogenadsorption method or the like, however, there is a possibility that theelectrolyte cannot penetrate into the portions of minute pores andtherefore the portions may not contribute to the contact with theelectrolyte, so the area of such portions is excluded. Therefore, it canbe said that in order to obtain a battery with good outputcharacteristics, the cathode active material needs to contain many poreshaving a certain size into which the electrolyte can penetrate.

In case that the cathode active material is composed of secondaryparticles that are an aggregate of primary particles and the primaryparticles are fine particles, many pores that exist between the primaryparticles are widely distributed in the cathode active material,however, these pores are minute, so the electrolyte cannot penetrateinto these pores, and thus the surface area that can come in contactwith the electrolyte does not increase.

Together with increasing the size of the primary particles, the diameterof the pores that exist between primary particles becomes larger and thepercentage of the pores through which electrolyte can penetrateincreases, however, it is presumed that the number of pores that aredistributed becomes small. Furthermore, when the primary particlesbecome too coarse, the percentage of space occupied by pores in theparticles greatly decreases, which causes the penetration paths ofelectrolyte to decrease, so this causes a drop in outputcharacteristics. Therefore, by making the size of the primary particlewithin a certain range, and creating many pores through which theelectrolyte can penetrate, it is possible to increase the surface areathat can come in contact with the electrolyte.

As an index of the size of the primary particles inside the cathodeactive material, the average particle size of primary particles can beused, however, the single crystals of the primary particles increase andso the particle size of the primary particles also increases, so thecrystallite diameter, which is an index of the size of the singlecrystals, is suitable. By making the primary particles a certain size,the size of the pores between primary particles becomes larger, andpenetration paths of the electrolyte to penetrate into the cathodeactive material are secured, and thus it becomes possible for theprimary particles exiting inside the cathode active material to come incontact with the electrolyte.

On the other hand, in order to increase the area of contact of thecathode active material with the electrolyte, it is also necessary tomake the surface area of the primary particles themselves greater. Inother words, by securing the penetration paths for the electrolyte topenetrate into the cathode active material, the number of primaryparticles that can come in contact with the electrolyte is increased,and by increasing the surface area of each individual primary particles,it is possible to greatly increase the surface area of the cathodeactive material with which the electrolyte comes in contact.

By making the single crystals of the primary particles larger, theparticle size of the primary particles is increased and the penetrationpaths for the electrolyte are secured, and by creating relatively largeunevenness on the surface of the primary particles, it is possible toincrease the effective surface area. This is because primary particlesare considered to be composed of single crystals, and as the singlecrystals become larger, the difference in the particle size betweensingle crystals that are exposed on the surface becomes larger, and as aresult, it is conceivable that the size of the unevenness on the surfaceof the primary particles will become larger. By uses the crystallitediameter as an index in this way, it is possible to evaluate both thesecuring of penetration paths for the electrolyte, and the effectivesurface are of the primary particles.

The crystallite diameter is normally found by Scherrer calculation givenby equation (1) below. The crystal surface that is used in thecalculation can be arbitrarily selected, however, in the ease of lithiumnickel composite oxide, the surface (00n), which is a plane directionthat is perpendicular to the layers of the layered structure throughwhich lithium ions intercalate, is appropriately applied because thepeak strength of the X-ray diffraction pattern is large, andfurthermore, (003) plane having a particularly strong peak strength ismore appropriately applied.

D=0.9λ/β cos θ  (1)

D: Crystallite diameter (Å)

β: Spread of the diffraction peak due to the crystallite size (rad)

λ: X-ray wavelength [CuKα] (Å)

θ: Diffraction angle (°)

In the present invention, the crystallite diameter at (003) plane of thelithium nickel composite oxide that was found through X-ray diffractionand the Scherrer equation is controlled so as to be in the range 1200 Åto 1600 Å and preferably 1200 Å to 1500 Å. When the crystallite diameterat (003) plane of the lithium nickel composite oxide is less than 1200Å, the primary particles are fine, and thus the pores existing betweenthe primary particles inside the cathode active material becomes minute,so it becomes impossible for the electrolyte to penetrate into thecathode active material, and thus sufficient contact area with theelectrolyte cannot be obtained. On the other hand, when the crystallitediameter at (003) plane is greater than 1600 Å, the primary particlesbecome to coarse, and the percentage of space that the pores occupyinside the secondary particles is greatly decreased, so the penetrationpaths for the electrolyte are decreased, and thus sufficient contactarea with the electrolyte cannot be obtained. Therefore, when thecrystallite diameter is less than 1200 Å or greater than 1600 Å, thecontact area with the electrolyte is decreased, so the outputcharacteristics are decreased. Furthermore, it is possible to obtain theobjective low-temperature output within the range of 1200 Å to 1600 Å,however, within the range of 1200 Å to 1500 Å, the output becomes flat,so in order to obtain stable low-temperature output, a crystallitediameter within this range is preferred.

The particle size of the primary particles is correlated with thecrystallite diameter at (003) plane, and by controlling the crystallitediameter within the range above, it is possible to control the particlesize of the primary particles so as to be in the preferred state.Moreover, preferably the particle size of the secondary particles issuch that the average particle size according to the laser diffractionscattering method is 5 μm to 20 μm, and particularly, 7 μm to 12 μm.

The cathode active material of the present invention is composed ofhexagonal crystals of lithium nickel composite oxide having a layeredstructure, however, in order to improve the thermal stability of thelithium nickel composite oxide, Co and Al are further added with a rangethat sufficient capacity can be obtained. More specifically, Co and Alare added so that the mole ratio with respect to the total amount of Ni,Co and Al is 0.05 to 0.3, and preferably; 0.1 to 0.2 for Co, and 0.01 to0.1, and preferably 0.02 to 0.05 for Al.

Furthermore, in order to improve the battery characteristics, as theadded element (M), at least one or more metal element selected from agroup consisting of Mg, Fe, Cu, Zn and Ga is added at a mole ratio of0.05 or less with respect to the total metal elements other than Li.

In the present invention, the precursor, which is the raw material ofthe cathode active material above, is a nickel composite hydroxide thatis expressed by the general expression;(Ni_(1-x-y)Co_(x)Al_(y))_(1-z)M_(z)(OH)₂ (where 0.05≦x≦0.3, 0.01≦y≦0.1,0≦z≦0.05, and M is at least one metal element selected from a groupconsisting of Mg, Fe, Cu, Zn and Ga), with the half width (full width athalf maximum) at (101) plane by X-ray diffraction of the nickelcomposite hydroxide being 0.45° to 0.8°. The structure of this precursoris the same as that of the cathode active material that is obtainedusing this precursor, and is already composed of secondary particlesthat are formed by an aggregate of primary particles.

From the aspect of improving the output characteristics, the precursoris preferably such that the surface of the hydroxide composed of Ni, Coand M as given in the expression above is covered by aluminum hydroxide.

The crystallite shape of the lithium nickel composite oxide of thecathode active material and that of the nickel composite hydroxide,which is a precursor, are correlated, and as the crystallinity of thenickel composite hydroxide becomes high, the crystallinity of theobtained lithium nickel composite oxide becomes high, and thecrystallite diameter also becomes larger. The lithium nickel compositeoxide is formed by lithium penetrating into the nickel compositehydroxide during calcination. Therefore, the crystallinity that isexpressed by the half width of the nickel composite hydroxide, or inother words the crystallite diameter thereof, is also maintained in thelithium nickel composite oxide, and by using a nickel compositehydroxide having high crystallinity, it is possible to obtain a lithiumnickel composite oxide having large crystallites.

In other words, by using a nickel composite hydroxide, whose half widthat (101) plane found by X-ray diffraction is 0.45° to 0.8°, as aprecursor, it is possible to obtain a lithium nickel composite oxidewhose crystallite diameter at (003) plane is 1200 Å to 1600 Å. When thehalf width at (101) plane by X-ray diffraction of the nickel compositehydroxide is less than 0.45°, the crystallite diameter of the lithiumnickel composite oxide becomes greater than 1600 Å. On the other hand,when the half width exceeds 0.8°, the crystallite diameter of thelithium nickel composite oxide becomes less than 1200 Å. Moreover, whenthe temperature during calcination is increased in order to increase thecrystallite diameter to 1200 Å or more when using a nickel compositehydroxide having a half width that is greater than 0.8°, sintering ofthe secondary particles occurs and the secondary particles becomecoarse, so the battery characteristics of the cathode active materialthat is obtained decrease. Therefore, in order to keep the crystallitediameter of the lithium nickel composite oxide within the range of 1200Å to 1500 Å, the half width of the nickel composite hydroxide ispreferably kept within 0.5°to 0.8°.

The crystal characteristics of the nickel composite hydroxide are foundby X-ray diffraction in the same was for the lithium nickel compositeoxide, however, in the present invention, the reason that the (101)plane was used is that half width at (101) plane changes a large amountdue to the manufacturing conditions, and particularly due to thecrystallization reaction conditions. It is possible to use the halfwidth of a crystal plane other than (101) plane as an index, however,the change due to manufacturing conditions is small, and there is apossibility that it will not be possible to sufficiently control thecrystallize size of the cathode active material that is obtained.

The manufacturing method for the cathode active material of the presentinvention is characterized by the precursor, or the precursor oxide thatis obtained by oxidizing roasting of that precursor, and the calcinationperformed in an oxidizing atmosphere after mixing with a lithiumcompound.

The manufacturing method for the precursor uses known technology(coprecipitation method or the like) for obtaining a metal hydroxide byneutralizing a metal salt aqueous solution, and the precursor isobtained by controlling the Ni solubility according to the pH,temperature, NH₃ concentration and the like of the reaction solutionduring the neutralization reaction.

In addition to nickel sulfate as the nickel salt of raw material, it ispossible to use nickel chloride, nickel nitrate or the like, as thecobalt salt, in addition to cobalt sulfate, it is possible to use cobaltchloride, cobalt nitrite or the like, and as the M metal salt, it ispossible to use the sulfate, a chloride, a nitrite or the like of thatmetal.

The conditions may change due to the manufacturing apparatus and thescale, however, specifically when using nickel sulfate as the nickelsalt, for example, the precursor above is obtained by controlling the Nisolubility of the reaction solution to be preferably 25 ppm to 100 ppmby mass, and more preferably 30 ppm to 80 ppm by mass by making the pHduring the neutralization reaction to preferably greater than 10 andless than 11.5, and more preferably between 10.6 and 11.0, thetemperature to be preferably 40° C. to 55° C., and more preferably, 45°C. to 55° C., and the NH₃ concentration of the reaction solution to be 5g/L to 20 g/L.

When the Ni solubility of the reaction solution is less than 25 ppm bymass, the amount of nuclei generated during the crystallization reactionincreases, and the half width at (101) plane of the obtained nickelcomposite hydroxide may exceed 0.8°. Moreover, when the Ni solubilityexceeds 100 ppm by mass, crystal growth during the crystallizationreaction is promoted, and the half width at (101) plane may become lessthan 0.45°.

On the other hand, when the Ni solubility of the reaction solution iscontrolled by the pH, temperature and NH₃ concentration of the reactionsolution during the neutralization reaction, and nickel sulfate is usedas the nickel salt, the Ni solubility becomes less than 25 ppm by masswhen the pH becomes 11.5 or greater, or the temperature becomes lessthan 40° C., or the NH₃ concentration in the reaction solution becomesless than 5 during the neutralization reaction. Moreover, the Nisolubility of the reaction solution becomes greater than 100 ppm by masswhen the pH becomes 10 or less, or the temperature becomes greater than55° C., or the NH₃ concentration in the reaction solution becomesgreater than 20 g/L during the neutralization reaction. When any one ofthe reaction conditions shifts from the specified value, the Nisolubility of the reaction solution shifts from the specified range, andin any case it is not possible to obtain a nickel composite hydroxidehaving the preferred crystallinity as the precursor for obtaining acathode active material having excellent battery characteristics.

The reaction conditions above are an example, and the even when the halfwidth at (101) plane exceeds the range above in those conditions due toeffects of the manufacturing apparatus and the scale of that apparatus,by referencing the relationship between the conditions above and thehalf width at (101) plane, it is possible to easily adjust the halfwidth at (101) plane according to those conditions.

As a manufacturing method for manufacturing the precursor above, thereis a coprecipitation method in which a mixed salt solution that includesa nickel salt, cobalt salt and M metal salt at specified ratios, andalkali aqueous solution are supplied to a reaction solution, such as pHregulated water so that the pH can be kept constant, and hydroxides ofthe nickel, cobalt and M metal are precipitated out. The ratios of theNi, Co and M the mixed salt solution can be determined according to thecomposition ratios in the lithium nickel composite oxide that is to befinally obtained as the cathode active material.

As described above, the nickel cobalt composite hydroxide that isobtained is secondary particles that are an aggregate of primaryparticles, however, preferably the shape of the secondary particles isspherical, and the secondary particles are adjusted so that the averageparticle size found from laser diffraction scattering is 5 μm to 20 μm.The shape of the particles and the average particle size can becontrolled by the mixing rate of the mixed salt solution and the alkaliaqueous solution, and the coprecipitation conditions.

Manufacturing of the nickel cobalt composite hydroxide is preferably bythe coprecipitation method described above, however, in addition tothat, the precursor above composed of secondary particles that areformed by an aggregate of primary particles can be obtained by a methodof manufacturing a nickel hydroxide by a crystallization method, andthen causing cobalt hydroxide to precipitate on the surface of thatnickel hydroxide, or by a method of pulverizing manufactured nickelcobalt composite hydroxide particles and obtaining the target particlesize by the spray drying method.

The nickel cobalt hydroxide that is obtained is filtered, washed anddried, however, these processes can be performed by normal methods.

The precursor above can also be a nickel composite hydroxide thatcontains Al and that is obtained by neutralizing a mixed salt solutionthat includes Al, however, in order to make the amount of Al containedin the each particle uniform, preferably, after the nickel compositehydroxide is obtained, that nickel composite hydroxide is covered byaluminum hydroxide.

For example, by making the nickel composite hydroxide a slurry, it ispossible to cover the nickel composite hydroxide with aluminum hydroxideby adding an aqueous solution that contains an aluminum salt such assodium aluminate, and mixing the slurry while adjusting the pH.Moreover, it is also possible to mix an aqueous solution containing adesired concentration of aluminum salt such as sodium aluminate to theslurry, and then adjust the pH and cause the aluminum hydroxide toadsorb into the surface of the particles of the nickel compositehydroxide,

The cathode active material of the present invention can be obtained bymixing the precursor obtained using the crystallization method above, ormixing an oxide of the precursor that is obtained by performingoxidizing roasting of that precursor with lithium, and then performingcalcination in an oxidizing atmosphere.

By performing oxidizing roasting of the precursor, it is possible toimprove the reactivity with lithium. In that case, the reaction with Lisufficiently advances in a short time, so it is possible to improveproductivity. The oxidizing roasting temperature is preferably 650° C.to 750° C., and more preferably 700° C. to 750° C. When the temperatureis less than 650° C., the oxide film that is formed on the surface isnot sufficient, and when the temperature exceeds 750° C., the surfacearea is too small, so the reactivity with Li decreases, which is notdesirable.

The oxidizing roasting atmosphere can be a non-reduced atmosphere withno problem, however, an air atmosphere or oxygen atmosphere ispreferred. The oxidizing roasting time and the furnace used forprocessing are not particularly limited, and can be appropriately setaccording to the amount being processed and the oxidizing roastingtemperature.

Mixing of the lithium compound is performed by mixing the precursor oran oxide of the precursor with lithium compound at the composition ratioof the lithium nickel composite oxide that will finally be obtained asthe cathode active material.

Mixing can be performed by using a dry mixer or granulator such as a Vblender, a Spartan granulator, Lodige mixer, Julia mixer, or verticalgranulator, and preferably mixing is performed in a suitable time rangefor uniform mixing.

Calcination is not particularly limited and can be performed using anormal method and apparatus, however, the temperature during calcinationis preferably 700° C. to 760° C., and more preferably 740° C. to 760° C.When the temperature during calcination is less than 700° C.,crystallinity of the lithium nickel composite oxide of the cathodeactive material is not sufficiently developed, and there is apossibility that the crystallite diameter at (003) plane will be lessthan 1100 Å. Moreover, when the temperature during calcination exceeds760° C., not only does the crystallite diameter at (003) plane of thelithium nickel composite oxide exceed 1600 Å, there is also apossibility that sintering of the secondary particles of the lithiumnickel composite oxide will occur and that that secondary particles willbecome coarse.

The calcination time is also not particularly limited, and as long asthe reaction described above proceeds sufficiently any amount of time isfine, however, preferably 1 to 10 hours is preferred. The oxidizingatmosphere is also not particularly limited, however, in order that thecrystallinity of the lithium nickel composite oxide is sufficientlydeveloped, an oxygen atmosphere that contains oxygen at 60% to 100% byvolume is preferred.

Moreover, when the rate of temperature increase to the calcinationtemperature is too fast, the lithium compound and the precursorhydroxide will separate, which is not desirable, and when the rate istoo slow, productivity worsens, so a rate of about 2° C./min to 5° C/minis realistic.

The lithium compound is not particularly limited, however, preferably isa lithium hydroxide or hydrate thereof. Lithium hydroxide has a lowmelting temperature and melts in the calcination temperature rangeabove, and the reaction is liquid phase-solid phase reaction, so it canreact sufficiently with a nickel composite hydroxide. When lithiumcarbonate is used, the lithium carbonate does not melt in thecalcination temperature range above, so there is a possibility that itwill not react sufficiently with the nickel composite hydroxide.

The non-aqueous electrolyte secondary battery of the present inventioncomprises a cathode active material layer that is formed using on thecathode active material above and layered on a cathode collector.

(a) Cathode

A cathode for a non-aqueous electrolyte secondary battery ismanufactured such as described below using the cathode active materialfor a non-aqueous electrolyte secondary battery described above.

First, powdered cathode active material, a conductive material, andbinding agent are mixed together, then a solvent, and preferably a waterbased solvent is added, and these are mixed and kneaded to form acathode mixture paste. The mixture ratios in the cathode mixture pasteare an important factor for setting the performance of the non-aqueouselectrolyte secondary battery. When the entire mass of the solid contentof the cathode mixture with the solvent removed is taken to be 100 partsby mass, as in the ease of a typical cathode for a non-aqueouselectrolyte secondary battery, preferably the content of the cathodeactive material is 80 to 95 parts by mass, the content of the conductivematerial is 2 to 16 parts by mass, and the content of the binding agentis 1 to 20 parts by mass.

The obtained cathode mixture paste is applied to the surface of acollector made of aluminum foil, dried and the solvent is dispersed. Asnecessary, pressure may be applied by a roll press to increase theelectrode density. A sheet shaped cathode can be made in this way. Thesheet shaped cathode is cut to an appropriate size according to theintended battery and provided for manufacturing the battery. The methodfor manufacturing the cathode is not limited to that described in thisexample, and can be manufactured by other methods as well.

When manufacturing the cathode, it is possible to use graphite (naturalgraphite, man-made graphite, expanded graphite, or the like), or acarbon black material such as acetylene black or Ketchen black.

The binding agent serves the role of holding together the activematerial particles, and is preferably a water-soluble polymer materialthat can dissolve in water. For example, a hydrophilic polymer such ascarboxymethyl cellulose (CMC), methyl cellulose (MC), cellulose acetatephthalate (CAP), hydropropyl methyl cellulose (HPMC), hydropropyl methylcellulose phthalate (HPMCP), polyvinyl alcohol (PVA), polyethylene oxide(PEO) can be used. Moreover, a water dispersible polymer can also beused. For example, a fluorine-based resin such aspolytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoro alkylvinyl ether copolymer (PEP), ethylene-tetrafluoroethylene copolymer(ETFE), vinyl acetate copolymer, styrene butadiene block copolymer(SBR), acrylic acid SBR resin (SBR latex), a rubber such as gum arabicor the like can be used. Of these, a fluorine-based resin such as PTFEis preferred.

The water based paste can be prepared by adding the cathode activematerial of the present invention, and the conductive material andbinding agent described above to a suitable water based solvent asadditives, then dispersing or dissolving these additive in the solventand mixing.

The prepared paste is applied to a cathode collector, then after thewater based solvent is volatilized and the paste is dried, the paste iscompressed. Typically, by using a coating apparatus (coater), the pastefor forming a cathode active material layer can be applied to thesurface of the collector at a specified thickness. The thickness of theapplied paste is not particularly limited, and can be appropriately setaccording to the shape and usage of the cathode and battery. Forexample, paste is applied to the surface of a foil that is 10 μm to 80μm thick, so that after drying the thickness is 5 μm to 100 μm. Afterthe paste has been applied, the coating is dried using a suitable dryer,to form a cathode active material layer having a specified thickness onthe surface of the collector. By pressing as desired the cathode activematerial layer that was obtained in this way, it is possible to obtain acathode sheet having the intended thickness.

(b) Anode

For the anode, an anode that is formed by mixing a binding agent with ananode active material such as metallic lithium or lithium alloy, or amaterial in which lithium ions can be adsorbed or desorbed, adding asuitable solvent to form a paste-like anode mixture, applying this anodemixture to the surface of a metal foil collector such as a coppercollector and drying, then as necessary compressing to increase theelectron density is used.

As the anode active material, it is possible to use a carbon materialsuch as natural graphite, man-made graphite, graphitized carbon, or acombination of these.

(c) Separator

A separator is placed in between the cathode and the anode. Theseparator separates the cathode and the anode, and holds theelectrolyte, and can be a thin film such as polyethylene, polypropyleneor the like, having a lot of micropore.

(d) Non-Aqueous Electrolyte

The non-aqueous electrolyte is an electrolyte made by dissolving alithium salt as a supporting electrolyte in an organic solvent.

As the organic solvent one type alone or a mixture of two types or moreselected from among (1) a cyclic carbonate such as ethylene carbonate,propylene carbonate, butylene carbonate, trifluoro propylene carbonateand the like; (2) a chain-shaped carbonate such as diethyl carbonate,dimethyl carbonate, ethyl methyl carbonate, dipropyl carbonate and thelike; (3) an ether compound such as tetrahydrofuran,2-methyltetrahydrofuran, dimethoxyethane and the like; (4) a sulfurcompound such as ethyl methyl sulfone, butane sulfone and the like; (5)and a phosphorus compound such as triethyl phosphate, trioctyl phosphateand the like.

As the supporting electrolyte, it is possible to use LiPF₆, LiBF₄,LiClO₄, LiAsF₆, LiN(CF₃SO₂)₂ and the like, and compounds of these. Theconcentration of the supporting electrolyte can be the same as that ofan electrolyte used in a conventional lithium ion secondary battery, andis not particularly limited. It is possible to use an electrolyte thatcontains a suitable lithium compound (supporting electrolyte) at aconcentration of 0.1 mol/L to 5 mol/L.

Furthermore, the non-aqueous electrolyte can also include a radicalscavenger, a surfactant, a flame retardant and the like.

(e) Battery Shape and Construction

The shape of a non-aqueous electrolyte secondary battery of the presentinvention that is composed of the cathode, anode and separator explainedabove can be various shapes such as a cylindrical type, laminated typeand the like.

Regardless of the shape used, the cathode and the anode are laminated byway of the separator to form electrodes, and the non-aqueous electrolyteis impregnated into the obtained electrodes, power collection leads areused to connect between the cathode current collector and the cathodeterminal that extends to the outside, and between the anode currentcollector and the anode terminal that extends to the outside, thensealed in a battery case to complete the non-aqueous electrolytesecondary battery.

The non-aqueous electrolyte secondary battery of the present inventionuses as a cathode active material the cathode active material for anon-aqueous electrolyte secondary battery of the present inventionhaving crystallinity where the crystallite diameter at (003) plane thatis found by X-ray diffraction and the Scherrer equation to be within therange 1200 Å to 1600 Å, so, for example, the low-temperature output in alow-temperature environment of −30° C. is improved by 20% or more whencompared with a conventional non-aqueous electrolyte secondary battery.

EXAMPLES

In the examples described below, a non-aqueous electrolyte secondarybattery, in which a cathode active material that is manufactured so thatthe crystallinity of the lithium metal composite oxide, or morespecifically, the crystallite diameter at (003) plane is adjusted to asuitable size is used as the cathode active material, was manufactured,and the performance was evaluated.

Example 1 (1) Cathode Active Material

First, the cathode active material was manufactured by the followingmethod. In other words, nickel sulfate (NiSO₄) used as a nickel supplysource and cobalt sulfate (CoSO₄) used as a cobalt supply source weremixed so that the mole ratio Ni:Co became 85:15, and a mixed nickelcobalt salt solution having a total of nickel and cobalt of 104.5 g/Lwas prepared.

Next, as the reaction solution, the mixed salt solution above, 25% bymass ammonia hydroxide (NH₃) aqueous solution and 25% by mass sodiumhydroxide aqueous solution (NaOH) were added to pure water that wasadjusted to a temperature of 50° C. and a pH of 11 at this temperature,and while maintaining the solution at that temperature and pH at thistemperature, the solution was supplied a little at a time to crystallizethe nickel cobalt composite hydroxide to form a nickel cobalt compositehydroxide slurry. The Ni solubility of the reaction solution duringcrystallization was measured and found to be 40 ppm by mass. Moreover,the NH₃ concentration of the reaction solution during crystallizationwas constant at nearly 10 g/L. This slurry was washed, filtered and thendried at approximately 70° C. to obtain a nickel cobalt compositehydroxide (Ni_(0.85)Co_(0.15)(OH)₂) powder.

The nickel cobalt composite hydroxide is dispersed into an aqueoussolution, in which sodium hydroxide (NaOH) and 20 g/L of sodiumaluminate (NaAlO₂) have been dissolved, to prepare a slurry, then whilestirring, the slurry is neutralized with a sulfuric acid aqueoussolution (H₂SO₄), and aluminum hydroxide is caused to precipitate outonto the surface of the nickel cobalt composite hydroxide. Nearly theentire amount of the sodium aluminate was precipitated out as aluminumhydroxide. The slurry was then washed, filtered and dried atapproximately 100° C., and then heated in an air atmosphere at 700° C.for 5 hours, and by performing oxidizing roasting, a nickel cobaltaluminum composite oxide (Ni_(0.82)Co_(0.15)Al_(0.03)O) was formed.

In order to evaluate the crystallinity, the half width at (101) plane ofthe obtained nickel cobalt aluminum composite oxide was measured usingan X-ray diffractometer (X'Pert PRO, manufactured by PANalytical) andfound to be 0.662°. The result is given in Table 1.

Next, lithium hydroxide (LiOH) as a lithium supply source is mixed withthe nickel cobalt aluminum composite hydroxide above so that the moleratio of Li and all of the other metal element (Ni, Co, Al) Li(Ni+Co+Al)becomes 1.05, to prepare raw material mixture for a lithium nickelcomposite oxide. After the raw material mixture was prepared, that rawmaterial mixture was calcinated in an oxygen atmosphere at 750° C. for 7hours to form a lithium nickel composite oxide(Li_(1.04)(Ni_(0.82)Co_(0.15)Al_(0.03))O₂) and obtain the cathode activematerial.

The half width at (003) plane of the obtained cathode active materialwas measure in the same way using an X-ray diffractometer, and byperforming Scherrer calculation using the obtained half width at (003)plane, the crystallite diameter at (003) plane was found to be 1346 Å.This result is given in Table 1.

(2) Non-Aqueous Electrolyte Secondary Battery (Lithium Ion SecondaryBattery) (2-1) Cathode

Using the obtained cathode active material, a water based paste wasprepared. In other words, when forming the cathode active material layeron the cathode, the cathode active material, acetylene black as theconductive material, and carboxymethyl cellulose (CMC) andpolytetrafluoroethylene (PTFE) as the binding agent were mixed until themass ratios of these materials became 88:10:1:1, and these materialswere added to a water based solvent (ion-exchanged water) so that thesolid content of the material became 54% by mass. Next, the materialswere mixed for 50 minutes using a planetary mixer, and the water basedpaste for the cathode active material layer was obtained.

Next, the obtained water based paste is applied to both surfaces ofaluminum foil having a thickness of 15 μm as the cathode collector sothat the total applied amount (solid content) was 9.5 g/cm². After themoisture content of the applied paste was dried, the paste was pressedinto a sheet shape by a roller press so that the layer thickness (entirethickness including the thickness of the cathode collector) was 60 μm,and by forming a cathode active material layer, a cathode (cathodesheet) for a lithium ion secondary battery was created.

(2-2) Anode

Graphite (coated with amorphous carbon) used as the anode activematerial, styrene-butadiene rubber (SBR) and carboxymethyl cellulose(CMC) used as the binding agent were mixed with ion-exchanged water sothat that ratios of these materials was 98:1:1, and a paste for formingan anode active material layer was prepared.

Next, the paste was applied to both surfaces of copper foil having athickness of 10 μm as the anode collector so that the total amount ofapplied paste (solid content) was 9.0 g/cm². After the moisture contentin the applied paste was dried, an anode (anode sheet) for a lithium ionsecondary battery was made by pressing the paste into a sheet shape witha roll press to a thickness (total thickness including the thickness ofthe anode collector) of 60 μm to form an anode active material layer.

(2-3) Lithium Ion Secondary Battery

The cathode sheet and the anode sheet were layered together with twoporous separators and wound, and by pressing from the laminateddirection, an electrode structure was formed into a flat shape. Next,the electrode structure was housed in a battery case, and a non-aqueouselectrolyte formed by dissolving a supporting electrolyte LiPF₆ having aconcentration of 1 mol/L in to a mixed solvent of ethylene carbonate(EC) and dimethyl carbonate (DMC) at a volume ratio of 1:1 filled intothe case. After that, collector leads that extend to the outside whereconnected between the cathode collector and anode collector, and thebattery case was sealed to make the lithium ion secondary battery.

(2-4) Evaluation

Evaluation was performed by investigating the output characteristics ofthe lithium ion secondary battery above in low-temperature conditions.In other words, after constant current discharge at a temperature of 25°C. to a voltage of 3.0 V, charging was performed at a constant currentand constant voltage to prepare a 40% SOC (State of Charge). After that,at −30° C., the current was appropriately changed and the voltage wasmeasure 2 seconds after the start of discharge, to create a I-Vcharacteristic graph of the sample battery was created. The dischargecut voltage was taken to be 2.0 V. From this I-V characteristic graphthe output value (W) was found to be 124 W. The evaluation results aregiven in Table 1.

Example 2

Except that the pH during crystallization of the nickel cobalt compositehydroxide was adjusted to 10.5, the cathode active material was obtainedin the same way as in Example 1 and evaluated. The Ni solubility of theslurry during crystallization was 80 ppm by mass. The half width at(101) plane of the precursor was 0.471°, the crystallite diameter at(003) plane of the cathode active material was 1589 Å, and the outputvalue at −30° C. of the lithium ion secondary battery was 121 W. Theresults are all given in Table 1.

Example 3

Nickel sulfate (NiSO₄) as the nickel supply source, cobalt sulfate(CoSO₄) as the cobalt supply source, and magnesium sulfate (MgSO₄) as aMg supply source were mixed to a mole ratio Ni:Co:Mg of 83:14:3, and anickel cobalt magnesium mixed salt water solution was prepared so thatthe total of nickel, cobalt and magnesium was 106.3 g/L.

Next, pure water that was prepared at a temperature of 50° C. and pH of11 at this temperature as a reaction solution, the mixed salt solutionabove, 25% by mass ammonia aqueous solution (NH₃) and 25% by mass sodiumhydroxide aqueous solution (NaOH) were supplied a little at a time tothe pure water, and while maintaining the above temperature and the pHat this temperature, crystallization of the nickel cobalt magnesiumcomposite hydroxide was performed to prepare a nickel cobalt magnesiumcomposite hydroxide slurry. The Ni solubility during crystallization wasmeasured and found to be 35 ppm by mass. Moreover, the NH₃ concentrationof the reaction solution during crystallization was nearly constant at10 g/L. This slurry was washed and filtered, then dried at approximately70° C. to obtain a nickel cobalt magnesium composite hydroxide(Ni_(0.83)Co_(0.14)Mg_(0.03)(OH)₂) powder.

The nickel cobalt magnesium composite hydroxide was dispersed in anaqueous solution, in which sodium hydroxide (NaOH) and 20 g/L of sodiumaluminate (NaAlO₂) were dissolved, to prepare a slurry, then the slurrywas neutralized while stirring with sulfuric acid aqueous solution(H₂SO₄), and the aluminum hydroxide was precipitated out onto thesurface of the nickel cobalt magnesium composite hydroxide. Nearly theentire amount of sodium aluminate was precipitated out as aluminumhydroxide. This slurry was then washed, filtered and dried atapproximately 100° C., after which oxidizing roasting was performed byheating at 700° C. in an air atmosphere for 5 hours, to form a nickelcobalt magnesium aluminum composite oxide(Ni_(0.81)Co_(0.13)Mg_(0.03)Al_(0.03)O).

Except for using this nickel cobalt magnesium aluminum composite oxide,the cathode active material was obtained and evaluated in the same wayas in Example 1. The half width at (101) plane of the precursor was0.508°, the crystallite diameter at (003) plane of the cathode activematerial was 1490 Å, and the output value at −30° C. of the lithium ionsecondary battery was 122 W. The results are all given in Table 1.

Comparative Example 1

Except for adjusting the pH during crystallization of the nickel cobaltcomposite hydroxide to a pH of 12.5, the cathode active material wasobtained and evaluated in the same way as in Example 1. The Niconcentration of the slurry during crystallization was 10 ppm by mass.The half width at (101) plane of the precursor was 0.958°, thecrystallite diameter at (003) plane of the cathode active material was967 Å, and the output value at −30° C. of the lithium ion secondarybattery was 89 W. The results are all given in Table 1.

Comparative Example 2

Except for adjusting the pH during crystallization of the nickel cobaltcomposite hydroxide to a pH of 10, the cathode active material wasobtained and evaluated in the same way as in Example 1. The Niconcentration of the slurry during crystallization was 200 ppm by mass.The half width at (101) plane of the precursor was 0.389°, thecrystallite diameter at (003) plane of the cathode active material was1728 Å, and the output value at −30° C. of the lithium ion secondarybattery was 112 W. The results are all given in Table 1.

Comparative Example 3

Except for adjusting the pH during crystallization of the nickel cobaltcomposite hydroxide to a pH of 11.5, the cathode active material wasobtained and evaluated in the same way as in Example 1. The Niconcentration of the slurry during crystallization was 20 ppm by mass.The half width at (101) plane of the precursor was 0.846°, thecrystallite diameter at (003) plane of the cathode active material was1123 Å, and the output value at −30° C. of the lithium ion secondarybattery was 119 W. The results are all given in Table 1.

TABLE 1 Half Width Crystallite Diameter Low- at (101) Plane at (003)Plane Temperature of Compoiste of Lithium Nickel Output hydroxide (°)Composite Oxide (Å) (W) Example 1 0.662 1346 124 Example 2 0.471 1589121 Example 3 0.508 1490 123 Comparative 0.958 967 89 Example 1Comparative 0.389 1728 112 Example 2 Comparative 0.846 1123 119 Example3

(Evaluation)

FIG. 1 illustrates the relationship between the crystallite diameter at(003) plane of the cathode active material and the low-temperatureoutput at −30° C., and it can be seen that there is a correlationbetween the crystallite diameter at (003) plane and the low-temperatureoutput at −30° C. In other words, in order to achieve stable highlow-temperature output, it is necessary for the crystallite diameter at(003) plane to be within the range 1200 Å to 1600 Å. Moreover, fromTable 1 it is understood that it is necessary for the half width at(101) plane of the nickel composite hydroxide to be within the range0.45° to 0.8°.

1. (canceled)
 2. (canceled)
 3. A precursor of a cathode active material for a non-aqueous electrolyte secondary battery, comprising: a nickel composite hydroxide expressed by the general expression: (Ni_(1-x-y)Co_(x)Al_(y))_(1-z)M_(z)(OH)₂ where 0.05≦x≦0.3, 0.01≦y≦0.1, 0≦z≦0.05, and M is at least one metal element chosen from Mg, Fe, Cu, Zn and Ga, and where the half width at (101) plane found by X-ray diffraction is 0.45° to 0.8°.
 4. The precursor of a cathode active material for a non-aqueous electrolyte secondary battery according to claim 3, wherein the precursor is obtained by covering the surface of a hydroxide composed of Ni, Co and M given by the expression above with aluminum hydroxide.
 5. The precursor of a cathode active material for a non-aqueous electrolyte secondary battery according to claim 3, wherein by mixing the precursor for obtaining a cathode active material for a non-aqueous electrolyte secondary battery with a lithium compound, or by mixing the precursor after oxidizing roasting with a lithium compound, and performing calcination of the obtained mixture in an oxidizing atmosphere, the cathode active material for a non-aqueous electrolyte secondary battery according to claim 1 is obtained.
 6. A manufacturing method for a cathode active material for a non-aqueous electrolyte secondary battery, comprising: mixing the precursor according to claim 3, or an oxide of the precursor that is obtained by performing oxidizing roasting of the precursor, with a lithium compound; and calcinating the obtained mixture in oxidizing atmosphere to obtain a lithium nickel composite oxide that is expressed by the general expression: Li_(w)(Ni_(1-x-y)Co_(x)Al_(y))_(1-z)M_(z)O₂ where 0.98≦w≦1.10, 0.05≦x≦0.3, 0.01≦y≦0.1, 0≦z≦0.05, and M is at least one metal element chosen from Mg, Fe, Cu, Zn and Ga, and where the crystallite diameter at (003) plane of the lithium nickel composite oxide that is found by X-ray diffraction and the Scherrer equation is within the range of 1200 Å to 1600 Å.
 7. The manufacturing method for a cathode active material for a non-aqueous electrolyte secondary battery according to claim 6, wherein the calcination temperature is within the range of 700° C. to 760° C.
 8. The manufacturing method for a cathode active material for a non-aqueous electrolyte secondary battery according to claim 6, wherein the lithium compound is lithium hydroxide.
 9. (canceled) 